Shoe stiffener and process of making the same



. 4, 1945. E. 1.. BECKWITH ETAL SHOE STIFFENER AND PROCESS OF MAXI HG THE SAME File d Jan. 21. 1941 Profecfed Adhesive Cenfers @waLw Patented Dec. 4, 1945 -SlIOE STIFFENER AND raoonss OF MAKING 'rns SAME Edwin L. Beckwlth, Brookline, and Adelbert P. Swett, Westwood. Mass, assignors to Beckwlth Manufacturing Company, Dover, N. 11., a corporation of New Hampshire Application January 21, 1941, Serial No. 375,204 (CI. 36-77) 12 Claims. The present invention, in one aspect, consists in a new and improved shoe stiffener of the heat responsive type. It includes within its scope,

however, the novel process herein disclosed of making shoe stifieners or sheet material having latent adhesive characteristics, as well as the novel sheet material itself.

Shoe stiifeners of the type to which our inve tion relates have been made heretofore bysaturatmg or coating a fabric base with molten blend or mixture of waxes, resins, rubber and the like, thus providinga thermosplastic blank which is stiff under normal conditions of temperature, but which may be rendered temporarily plastic and adhesive to a mild degree by the application of moderate heat in the shoemaking process. It is desirable that shoe stilfeners, particularly box toes, should provide in the completed shoe a hard, tough, resilient arch and also that the box toe blank should be united in a permanent adhesive bond to the contiguous parts of the upper. The resinous compounds heretofore used tend to be brittle, particularly during winter conditions, and-a bond depending upon them I alone is likely to be fractured during the multiple shocks which a shoe normally receives in wear. Thus, even though the adhesion of such a stiffener, for example to the lining and doubler or lining and upper leather may appear satisfactory when the shoe is first made, it may nevertheless lack permanence, and failure is likely to allow the lining to sag or bag down on the toes of the wearer or at least to loosen and wrinkle. It is moreover, important that shoe stiffener blanks should not, atnormal temperatures, be

- adhesive because then the blanks have a tendency to stick together or block when stacked for shipment or to soften or exude under conditions of summer heat. One object of the present invention is to combine in a shoe stiffener these hitherto incompatible characteristics and to provide a commercially satisfactory and desirable stiifener having optimum characteristics both in respect to its hardness and resiliency in the shoe and its capacity to form a permanent bond with the upp Shoe stiffeners have been known heretofore which comprise a base fabric impregnated with a soluble cellulose derivative and such stiifeners,

when treated withv a proper solvent, create a lacquer which serves. to cement the stiffener to the upper material with a more complete and enduring adhesive bond than it has been possible to produce heretofore where a-t hermoplast.c shoe stiffener is employed.

' carbons of high adhesive qualities with thermopensive and wasteful solvents to render it In one aspect our invention is of commercial importance because it supplies for the first time a thermoplastic shoe stiffener having all the adhesive bonding advantages of solvent-treated stiffeners but without requiring the use of exconformable during the lasting operation. The present invention therefore makes available to the shoemaker box toe stiffeners having the desirable characteristics of hardnes's'and resiliency obtainable in a thermoplastic stifiener together with a very desirable adhesive bonding characteristic heretofore only obtainable by using solvent-treated stiifeners.

Our invention is based on the discovery that it is possible to blend certain polymenzed hydroplastic ingredients in preparing an improved thermoplastic impregna-nt by proceeding in the following manner; that is to'say, by melting the thermoplastic ingredients while separated along the lines of their compatibility or incompatibihty with respect to the adhesive addition-product that wehave found it desirable to add. We prefor to use polymerized hydrocarbons of straightchain structure, especially rubber-like polymers of isobutylene sold generally under the trade name Vistanex, although we may employ oxidized linseed oil, sulphonated corn oil, phtnallic anhydride-glycerin-fatty acid polymerization products such as -Duraplex N. D. 75," "Paraplex AL 16," alkyd type resins such as condensation products involving polybasic acids and polynydr'ic alcohols and the like.

Dealing specifically with polyisobutylene we .have found this to be compatible with rosin, but

to be less compatible with certain gums, waxes, and the like. By compatib.e we mean that polyisobutylene has the characteristic of forming with rosin a smootn homogeneous molten mixture or emulsion without tending to cause precipitation of any ingredient. Accordingly havingsepaiated our ingredients on the basis as,

suggested abo we, we render molten those that are compatible with our polyisobutylene. Based on the entire completed batch we add to the compat1b.e ingredients between one-eighth of one percent and six or seven percent of poiyisobutylone, the variation depending upon the results it is desired to produce.

The molten, mass is stirred or agitated until t. e polyisobutylene .s in apparent solution, that is to say, when a sample of the mo.ten bath,

flowed from a ladle for example. shows no graininess or separate particulation. At this point, the

or segregate cipitation may comprise small agglomerates or,

yunderideal conditions, may'have a particle size base fabric may through the'bath gredient, such as particles and that thus and transported without the as small asrseven microns. I

When. thoroughly molten, any desired web or be immersed in and passed and subsequently cooled to conform to the usual shoe stiffener practice. Upon examination the adde polyisobutylene, is found to be distributed throughout the entire sheet, but, either due to filtration on the surface of the fabric base or poss'i-blydue to the diverse electronic charge of the fibresandthe adhesive ingredient in it is localized andidentifiable at the surface in spots or specks of infinitesimal size.

If such an adhesive were present on the fabric d precipitated adhesive inv ent's, makeup about 60% 2,890,847 gum, wax and rubber ingredients hitherto set ployed in accordance with our invention is as follows:

Percent- 888 Ingredient Montan wax; IIIIIIII Rubber.(srlnoked sheet or crepe).

.Gum cop 2. 6 Polylsobutylene From the foregoing, formula it will benoted that the rosin, calciumjresinate ene, which are themutually compatiblezingrediof the complete -mixture,flwhileth e incompatible ingredients constitute the remaining 40%. the-bestnow known to surface in exposed or unprotected condition, the sheets of material stacked one on the other for transportation, or alternatively rolled into a coil, would weld and fuse together and thus be impractical to handle. We have found, however, that the liquid ner as to provide a coating of extremely thin measurement between and over the adhesive our shoe stiiiener material may be; stored blocking or fusing of one sheet to another.

When after the normal subsequent operations of cutting and skiving, such a stiffener is heated in the shoe factory, we find the overlying and surrounding film of normal compoundmelts away or withdraws itself, exposing innumerable particles of our adhesive. In this naked condition the shoe stiffener is incorporated into the shoe upper and the subsequent adhesion to contiguous'surfaces is inevitably achieved in a permanent and highly desirable manner.

Furthermore, it has long been noted by us that many thermoplastic shoe stiffeners commercially used attain a higher degree of adhesion when softened by dry heat than when softened by steam or moist heat. This we believe to be due to the condensed film of water deposited when steam is the heating medium; yet steam is in general more readily available to the shoemaker and more generally used than is dry heat. Our new and improved stifiener attains equ lly good adhesion in the upper whether dry or wet heat i employed and it thus allows greater flexibility and freedom to th shoemaker and gives a greater guarantee of uniform and satisfactory results in use.

These and other characteristics of our invention will be best understood and appreciated from consideration of the following specific example selected for purposes of illustration. A box toe stiffener exemplifying our invention is shown in the accompanying drawing in which- Fig.1 isa plan view representing a portion of the stiffener as. seen in the field of a micro, scope, and v I Fig. 2 is a fragmentary view showing the stiffener partially separated from the liningo; upper. 1 One illustrative formula which may be bath now solidifies in such a manus the percentages of thei'various ingredients may be varied to meet different industrial requirements all within the scope of our invention.

In proceeding under the formula above given the rosin, which may be any commercial rosin, is first reduced to molten condition and the polyisobutylene is added to the molten bath followed by the addition of limed rosin or calcium resinate as a hardener to raise the melting point of the entire mix. These three ingredients are compatible and form a smooth, homogeneous molten solution in which no tracev of the polyisobutylene is visible. The gum copal is next added to the molten 'bath and with the addition of this ingredient a slight granulation may be detected therein. The montan wax, or in its place any hard wax, and rubber ingredients may now be added I tected due to a precipitation or coagulation of the polyisobutylene. The particle size of the polyisobutylene, as already noted is extremely fine, that is, in the order of 6 or 8 microns and these particles are apparently distributed more or less uniformly throughout the molten bath.

Any desired fabric base may be employed in providing the sheet material from which to form the shoe stifieners such for example, as wool felt or Windsor cloth. The base is passed through the molten bath and thereby saturated and coated with the molten material. This is then cooled and indurated by the stifieningof the impregnant at normal temperature.- The polyisobutylene particles as already noted ar distributed throughout the surfaces of the sheet material as adhesive centers and these are protected by a thinsurface film of the wax-rosin-rubber. ingredients of the impregnant. They thus exist as a multiplicity of generally distributed adhesive centers or points protected for the timebeing so that in the normal handlin and storage of the sheets even at summer temperature, there is no objectionable tendency of the sheets to stick together or to exude adhesive. Subsequently th indurated sheets may be cut into box toe or counter blanks and skived as is customary for shoemaking requirements.

In Fig. 1. of the drawing a box toe blank I0 is shown and a portion of the blank is represented somewhat conventionally and imaginatively as seen inf-the field of a microscope presenting a multiplicity of protected adhesive centers in its surface. In Fig.2 the blank I0 is represented as havin from a' the lining of a shoe upper. 'In this operation vacuumand polyisobutyl- While this formula is been heated and then partially separated portion I! of the woven textile fabric of many of the adhesive centers in the box toe blank are drawn out as a group of rubber-like adhesive threads ll. If the blank is heated and momentarily doubled on itself this phenomenon of a multiplicity of extremely fine connecting threads may be observed, while of course, at normal temperature no such adhesive bonding occurs.

Whether or not the specific ingredients named are theoretically. more or less compatible with the adhesive hydro-carbon used in the molten mixture, nevertheless it is our intention to blend into the molten bath polyisobutylene with these ingredients which we have found in practice to result in a smooth homogeneous solution and then to bring about a dispersion of the polyisobutylene particles by adding to the molten bath ingredients that have the desired reaction in the solution.

We have disclosed herein one process of producing a heat-responsive shoestiffener in which an adhesive ingredient is present in non-continuous phase. Such a stiffener is a novel article of manufacture and is claimed as ourinvention by whatever process it may be produced.

Moreover, sheet material having adhesive'ingredients present in discontinuous phasecand in protected condition in available throughout its surface is not-limited in'its use to shoe stiifeners but may be advantageously employed in adhesive tape or wherever sheet material of latent adhesive characteristics is required. For example, it may take the place of adhesive tape or sheets now supplied with a mask; ing ply which must be removed and wasted to make the adhesive surface accessible. In the material of our invention the protective film or 1 sheet may be removed by heat, pressure or by scraping or otherwise.-

Having thus disclosed our invention and described certain specific embodiments thereof for purposes of illustration, but not in any limiting and desire to secure by sense, we claiin as new letters Patent:

1.- The process of making shoe stiffeners, which consists in first making a homogeneous solution of, the polyisobutylene Vistanex in 'a molten compatible resinous medium, adding to the ho-; mogeneous solution a lesser amount. of an incompatible heat-responsive stiffening gum and thereby precipitating the Vistanex as discrete particles in the molten bath, impregnating a fabric base therein, cooling and stiffening the impregnated material thus rendering it normally iron-adhesive, and cutting shoe stifieners thererom. Y

2. The process of making shoe stiffening material, which includes the. steps of first making a homogeneous solution of' polyisobutylene in a molten compatible resinous stiffening medium, precipitating the polyisobutylene by adding to the homogeneous solution a smaller amount of an incompatible resinous stiffening ingredient, saturating and coating a fabric base with the molten mixture, thereby distributing isolated particles of polyisobutylene thereupon, and then cooling the treated fabric thereby rendering it normally nonadhesive.

3. The process of making shoe stiffening material, which consists in making a smooth homogeneous solution of a polymerized hydrocarbon of high adhesive quality selected from the group isobutylene, oxidized linseed oil, sulphonated corn oil, phthallic anhydride-glycerin-fatty acid polymerization products, alkyd type resins and polyhydric alcohols in a compatible resin, precipitatlocations' I non-tacky surface film.

ing the hydrocarbon by adding to the molten bath a hard wax which is incompatible with the said hydrocarbon, and then saturating a fabric base in the molten mixture and cooling it, thereby distributing upon the base adhesiveparticles of the hydrocarbon which are protected by an indurated 4. .The process of making shoe stifl'ener material, which consists in dispersing a polymerized hydrocarbon selected from the group isobutylene, oxidized linseed oil, sulphonated corn oil, phthallic anhydride glyoerin-fatty acid polymerization products, alkydtype resins and polyhydric alcohols in a molten bath of a compatible resin, precipitating said hydrocarbon. in discrete par-' ticles by adding to the molten bath a smaller amount of hard wax and rubber ingredients which are incompatible with the hydrocarbon, and then saturating a fabric base in the molten mixture and cooling it, thereby distributing a multiplicity of adhesive hydrocarbon particles protected by a non-adhesive film over both surfaces of the base.

5. The process of making shoe stiffener material, which consists in making a homogeneous so; Q

lution of approximately 2 /2% or the polyisobutylene Vistanexj' 37 /2% molten rosin and 20% calcium resinate, subsequently adding about 10% gum copal and about 30% montan wax and rubber to the molten bath and thereby precipitating the Vistanex as discrete particles in the molten bath, then impregnating a fabric base therein and thereby distributing the Vistanex particles as adhesive centers throughout both faces of the material and then cooling the impregnated fabric,

thus rendering it normally non-tacky.

' 6. A shoe stiffener comprising a fabric base coated and saturated with an indurated mixture of resin and wax includingas approximately 2% of the whole a multiplicity of particles or apolymerized hydrocarbon of high adhesive quality distributed throughout its surface and protected at normal temperature by a superficial indurated non-adhesive film of a resin-wax mixture.

7. A heat-responsive shoe stiffener, comprising a fabric base carrying. a normally stifi and nonadhesive heat-responsive resin-wax impregnation having an adhesive ingredient comprising about 2% of a polymerized hydrocarbon of high adhesive quality distributed in separate spots therein and protected by a hard surface film of said impregnation.

8. A shoe stiflener comprising a fabric base carrying a normally stiff and normally heat-responsive resin-wax impregnation, said impregnant having distributed beneath its surface a multiplicityv of adhesive centers comprising'a polymerized hydrocarbon of high adhesive quality so dispersed as to become accessible to surface contact when a stiffener is heated and the surface layer of the stiff impregnant removed from its protecting relation to the said adhesive centers.

9. The sheet material forshoe stiifeners or the like having latent adhesive characteristics and comprising a thin flexible base fabric coated and saturated with an indurated mixture of resin and wax and having a multiplicity of adhesive particles of a polymerized hydrocarbon of high ad- I hesive quality distributed throughout its'surface and protected by a thin removable and normally non-adhesive film of the said indurated mixture. 10.Sheet material for shoe stiffeners or the normally stiff and non-adhesive, but having latent adhesive characteristics and comprising a thin flexible base of fabric coated and saturated withamixtureofwaxandrosmontheonelnnd, f

and a polymerized hydrocarbon o1 highadhesive quality immiscible therewith, on the other hand,

blended and disp rsed one in the other and inadurated by the former ingredients and with a surface film thereof masking the hydrocarbon ingredient.

11. A heat-responsive shoe stiiIener, including in its structure atabric base having in its composition a non-continuous adhesive ingredient consisting or a-polymerized hydrocarbon of high adhesive quality protected at normal temperature by an indurated him or non-adhesive resin-wax mixture.

12. A heat-responsive shoe stiffener, including in its structure a fabric base having poiyisobutylene distributed in its composition as a non-continuous adhesive ingredient protected at normal temperature by an indurated him 01' non-adhesive rosin and montan wax.

EDWIN L. BECK WITH. ADELBERT P. SWE'IT. 

